Airworthiness certification requirements for transport category aircraft under Part 25 of the US Federal Aviation Regulations (FARs, 14 CFR) and other equivalent international certification requirements typically require that aircraft structures withstand certain in-flight impacts, such as bird strikes, without experiencing airframe failure so that the aircraft can continue the flight and land safely. Components such as empennage leading edges (e.g., wings as well as horizontal and vertical stabilizers) are particularly critical components of the airframe. Thus, in order to comply with specific discrete source damage certification requirements of FAR Part 25 (incorporated hereinto by reference), the aircraft must withstand the impact of birds weighting 4 pounds (FAR §25.571 [e][1]) and 8 pounds (FAR §25.631).
In order to assure structural integrity of the empennage structure (as described in FAR §25.631, for example), one common engineering design has been to include an additional device colloquially called a “splitter plate” physically inside the leading edge which is attached rigidly to the empennage primary (spar) structure. In such a situation, the splitter plate is physically spaced from the leading edge so that if the leading edge collapses on impact with a bird in flight, the splitter plate will absorb the impact energy by splintering the bird thereby protecting the empennage primary structure. This traditional option of providing a splitter plate in operative association with empennage leading edges works effectively, but extracts a substantial weight penalty as the splitter plate is usually in the form of a rigid structural component made from metal (e.g., aluminum or steel).
Other proposals have been made to provide impact resistant to aircraft leading edges. For example, one prior proposal has been made in International Patent Publication WO 2007/07138 (incorporated hereinto by reference) wherein an arcuate protective skin is provided which is formed of glass-fiber reinforced aluminum material that may optionally include a series of spaced apart rib stiffeners. US Patent Application Publication 2007/0138340 (incorporated hereinto by reference) proposes to provide a protective skin forming the leading edges of an aircraft structure which is chemically etched and/or mechanically milled in oval and rectangular patterns so as to create crumple zones to generate progressive failure of the metal upon an in-flight impact with an object.